From: Dave Hart Date: Tue, 30 Jun 2009 07:59:26 +0000 (+0000) Subject: driver20.html: X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=abd970ced93af71d44ad810725cbf4024d2b3e37;p=thirdparty%2Fntp.git driver20.html: note fudge flag1 now enables/disables (default) PPSAPI support make bitrate setting values more obvious to those not fluent in binary shifting ChangeLog: punctuation bk: 4a49c5den58nFV2drOpY20VcXdQlfQ --- diff --git a/ChangeLog b/ChangeLog index 3d5ad48f25..148319f4c8 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,4 +1,4 @@ -* [Bug 1234] convert NMEA driver to use common PPSAPI code +* [Bug 1234] convert NMEA driver to use common PPSAPI code. * timepps-Solaris.h pps_handle_t changed from pointer to scalar * Spectracom refclock added to Windows port of ntpd (4.2.5p184) 2009/06/24 Released by Harlan Stenn diff --git a/html/drivers/driver20.html b/html/drivers/driver20.html index f85dab653a..c683743908 100644 --- a/html/drivers/driver20.html +++ b/html/drivers/driver20.html @@ -22,7 +22,7 @@

This driver supports GPS receivers with the $GPRMC, $GPGLL, $GPGGA, $GPZDA, and $GPZDG NMEA sentences by default.  Note that Accord's custom NMEA sentence $GPZDG reports using the GPS timescale, while the rest of the sentences report UTC.  The difference between the two is a whole number of seconds which increases with each leap second insertion in UTC.  To avoid problems mixing UTC and GPS timescales, the driver disables processing of UTC sentences once $GPZDG is received.

The driver expects the receiver to be set up to transmit at least one supported sentence every second.

The accuracy depends on the receiver used. Inexpensive GPS models are available with a claimed PPS signal accuracy of 1 ms or better relative to the broadcast signal. However, in most cases the actual accuracy is limited by the precision of the timecode and the latencies of the serial interface and operating system.

-

If the Operating System supports the PPSAPI, RFC-2783, it will be used.
 

+

If the Operating System supports PPSAPI (RFC 2783), fudge flag1 1 enables its use.
 

The various GPS sentences that this driver recognises look like this:
(others quietly ignored)

$GPRMC,UTC,POS_STAT,LAT,LAT_REF,LON,LON_REF,SPD,HDG,DATE,MAG_VAR,MAG_REF*CS<cr><lf>
@@ -64,9 +64,9 @@ $GPZDG,GPSTIME,DD,MM,YYYY,AA.BB,V*CS<cr><lf>
   <cr><lf> - Sentence terminator.

Specific GPS sentences and bitrates may be selected by setting bits of the 'mode' in the server configuration line:
-   server 127.127.20.x mode X
    bit 0 - process $GPMRC    (value = 1)
    bit 1 - process $GPGGA    (value = 2)
    bit 2 - process $GPGLL     (value = 4)
    bit 4 - process $GPZDA or $GPZDG    (value = 8)
+   server 127.127.20.x mode X
    bit 0 - process $GPMRC    (value = 1)
    bit 1 - process $GPGGA    (value = 2)
    bit 2 - process $GPGLL    (value = 4)
    bit 4 - process $GPZDA or $GPZDG    (value = 8)

The default (mode 0) is to process all supported sentences, which results in the last received each cycle being used.  Multiple sentences may be selected by adding their mode bit values.  The driver uses 4800 bits per second by default.  Faster bitrates can be selected using bits 4, 5, and 6 of the mode field:

-     bits 4/5/6 - select serial bitrate   ( 0 for 4800 - the default, 1 for 9600, 2 for 19200, 3 for 38400, 4 for 57600, 5 for 115200 )

+     bits 4/5/6 - select serial bitrate   (0 for 4800 - the default, 16 for 9600, 32 for 19200, 48 for 38400, 64 for 57600, 80 for 115200)

The driver will send a $PMOTG,RMC,0000*1D<cr><lf> command each poll interval.  This is not needed on most GPS receivers because they automatically send $GPRMC every second, but helps a Motorola GPS receiver that is otherwise silent.  NMEA devices ignore commands they do not understand.

Setting up the Garmin GPS-25XL

Switch off all output with by sending it the following string. @@ -88,11 +88,11 @@ $GPZDG,GPSTIME,DD,MM,YYYY,AA.BB,V*CS<cr><lf>
refid string
Specifies the driver reference identifier, an ASCII string from one to four characters, with default GPS.
flag1 0 | 1 -
Not used by this driver. +
Disable PPS signal processing if 0 (default); enable PPS signal processing if 1.
flag2 0 | 1 -
Specifies the PPS signal on-time edge: 0 for assert (default), 1 for clear. +
If PPS signal processing is enabled, capture the pulse on the rising edge if 0 (default); capture on the falling edge if 1.
flag3 0 | 1 -
Controls the kernel PPS discipline: 0 for disable (default), 1 for enable. +
If PPS signal processing is enabled, use the ntpd clock discipline if 0 (default); use the kernel discipline if 1.
flag4 0 | 1
Obscures location in timecode: 0 for disable (default), 1 for enable.